FIG. 6 shows a block diagram of a vibratory angular velocity sensor, one of conventional vibratory inertial force sensors, and the vibratory angular velocity sensor comprises the following elements:                sensor element 203 including driver section 201 and sensor section 202;        drive control circuit 204 for applying a control voltage to driver section 201, thereby vibrating sensor element 203, and then controlling the vibration; and        detection circuit 205 for processing a detection signal supplied from sensor section 202.        
In detection circuit 205, the detection signal supplied from sensor section 202 is differentially amplified by differential amplifier 206. The amplified signal and an inverted signal of the detection signal inverted by inverting amplifier 207 are synchronously wave-detected by synchronous wave detector 208. Then the resultant signal is smoothed by low-pass filter 209, so that the signal with disturbance noise, such as external impact, suppressed is output.
Conventional low-pass filter 209 firstly amplifies the signal having undergone the synchronous wave-detection with inverting amplifier 220 working as a pre-amplifier, then smoothes the resultant signal with smoothing circuit 221, or the signal is amplified and smoothed at the same time by an active filter (not shown).
The foregoing conventional vibratory inertial force sensor is disclosed in, e.g. Unexamined Japanese Patent Publication No. 2002-267448.
The signal having undergone the synchronous wave-detection in wave detector 208 of conventional vibratory inertial force sensor; however, draws a saw-tooth waveform as drawn by synchronous wave-detection output 208a shown in FIG. 7. At switchover section 210 of this waveform, the amplifying capacity of inversing amplifier 220 or the active filter working as a pre-amplifier of the low-pass filter cannot fully track the saw-tooth waveform, so that the waveform actually drawn by output 220a from the inversing amplifier becomes as shown in FIG. 7. In FIG. 7, the horizontal axis represents a time, and the vertical axis represents an electrical potential of respective output signals.
As shown in FIG. 7, output 220a supplied from the inverting amplifier and having undergone the amplification includes waveform error 212 which causes offset 211 at sensor output 205a having undergone the smoothing. Smoothing circuit 221 of low-pass filter 209 thus cannot implement an accurate smoothing process, so that the performance of the vibratory inertial force sensor is obliged to lower due to internal process within detection circuit 205.